View source for 1fev

[[Image:1fev.gif|left|200px]]

 {{Structure
|PDB= 1fev |SIZE=350|CAPTION= <scene name='initialview01'>1fev</scene>, resolution 2.25&Aring;
|SITE= 
|LIGAND= <scene name='pdbligand=AIB:ALPHA-AMINOISOBUTYRIC+ACID'>AIB</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene>
|ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/Pancreatic_ribonuclease Pancreatic ribonuclease], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.27.5 3.1.27.5] </span>
|GENE= 
|DOMAIN=
|RELATEDENTRY=[[1d5d|1D5D]], [[1d5e|1D5E]], [[1d5h|1D5H]], [[1rnv|1RNV]], [[1rbh|1RBH]]
|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1fev FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1fev OCA], [http://www.ebi.ac.uk/pdbsum/1fev PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1fev RCSB]</span>
}}

'''CRYSTAL STRUCTURE OF THE ALA4AIB MUTATION IN RNASE S'''


==Overview==
The S protein-S peptide interaction is a model system to study binding thermodynamics in proteins. We substituted alanine at position 4 in S peptide by alpha-aminoisobutyric acid (Aib) to investigate the effect of this substitution on the conformation of free S peptide and on its binding to S protein. The thermodynamic consequences of this replacement were studied using isothermal titration calorimetry. The structures of the free and complexed peptides were studied using circular dichroic spectroscopy and X-ray crystallography, respectively. The alanine4Aib replacement stabilizes the free S peptide helix and does not perturb the tertiary structure of RNase S. Surprisingly, and in contrast to the wild-type S peptide, the DeltaG degrees of binding of peptide to S pro, over the temperature range 5-30 degrees C, is virtually independent of temperature. At 25 degrees C, the DeltaDeltaG degrees, DeltaDeltaH degrees, DeltaDeltaS and DeltaDeltaCp of binding are 0.7 kcal/mol, 2.8 kcal/mol, 6 kcal/mol x K and -60 kcal/mol x K, respectively. The positive value of DeltaDeltaS is probably due to a decrease in the entropy of uncomplexed alanine4Aib relative to the wild-type peptide. The positive value of DeltaDeltaH: degrees is unexpected and is probably due to favorable interactions formed in uncomplexed alanine4Aib. This study addresses the thermodynamic and structural consequences of a replacement of alanine by Aib both in the unfolded and complexed states in proteins.

==About this Structure==
1FEV is a [[Protein complex]] structure of sequences from [http://en.wikipedia.org/wiki/Bos_taurus Bos taurus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1FEV OCA]. 

==Reference==
Structural and thermodynamic consequences of introducing alpha-aminoisobutyric acid in the S peptide of ribonuclease S., Ratnaparkhi GS, Awasthi SK, Rani P, Balaram P, Varadarajan R, Protein Eng. 2000 Oct;13(10):697-702. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/11112508 11112508]
[[Category: Bos taurus]]
[[Category: Pancreatic ribonuclease]]
[[Category: Protein complex]]
[[Category: Ratnaparkhi, G S.]]
[[Category: Varadarajan, R.]]
[[Category: aib]]
[[Category: alpha aminoisobutyric acid]]

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